<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

    </style>
</head>
<body>
    <button>按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <button>按钮5</button>
    <script>
        // 获取所有按钮元素
        var btns = document.getElementsByTagName('button')
        for(var i = 0; i < btns.length; i++ ) {
            btns[i].onclick = function() {
            // (1)先把所有按钮的颜色去掉
            for (var i= 0; i < btns.length; i++ ) {
                btns[i].style.backgroundColor = '';   
            }
            // (2)再把当前的按钮颜色变为pink
            this.style.backgroundColor = 'pink';   
            }
        }
    </script>
</body>
</html>